// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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package com.google.protobuf;

import static com.google.protobuf.Internal.checkNotNull;

import java.io.IOException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * Main runtime interface for protobuf. Applications should interact with this interface (rather
 * than directly accessing internal APIs) in order to perform operations on protobuf messages.
 */
@ExperimentalApi
final class Protobuf {
    private static final Protobuf INSTANCE = new Protobuf();

    private final SchemaFactory schemaFactory;

    // TODO(nathanmittler): Consider using ClassValue instead.
    private final ConcurrentMap<Class<?>, Schema<?>> schemaCache =
            new ConcurrentHashMap<Class<?>, Schema<?>>();

    /**
     * Gets the singleton instance of the Protobuf runtime.
     */
    public static Protobuf getInstance() {
        return INSTANCE;
    }

    /**
     * Writes the given message to the target {@link Writer}.
     */
    public <T> void writeTo(T message, Writer writer) throws IOException {
        schemaFor(message).writeTo(message, writer);
    }

    /**
     * Reads fields from the given {@link Reader} and merges them into the message.
     */
    public <T> void mergeFrom(T message, Reader reader) throws IOException {
        mergeFrom(message, reader, ExtensionRegistryLite.getEmptyRegistry());
    }

    /**
     * Reads fields from the given {@link Reader} and merges them into the message.
     */
    public <T> void mergeFrom(T message, Reader reader, ExtensionRegistryLite extensionRegistry)
            throws IOException {
        schemaFor(message).mergeFrom(message, reader, extensionRegistry);
    }

    /**
     * Marks repeated/map/extension/unknown fields as immutable.
     */
    public <T> void makeImmutable(T message) {
        schemaFor(message).makeImmutable(message);
    }

    /**
     * Checks if all required fields are set.
     */
    <T> boolean isInitialized(T message) {
        return schemaFor(message).isInitialized(message);
    }

    /**
     * Gets the schema for the given message type.
     */
    public <T> Schema<T> schemaFor(Class<T> messageType) {
        checkNotNull(messageType, "messageType");
        @SuppressWarnings("unchecked")
        Schema<T> schema = (Schema<T>) schemaCache.get(messageType);
        if (schema == null) {
            schema = schemaFactory.createSchema(messageType);
            @SuppressWarnings("unchecked")
            Schema<T> previous = (Schema<T>) registerSchema(messageType, schema);
            if (previous != null) {
                // A new schema was registered by another thread.
                schema = previous;
            }
        }
        return schema;
    }

    /**
     * Gets the schema for the given message.
     */
    @SuppressWarnings("unchecked")
    public <T> Schema<T> schemaFor(T message) {
        return schemaFor((Class<T>) message.getClass());
    }

    /**
     * Registers the given schema for the message type only if a schema was not already registered.
     *
     * @param messageType the type of message on which the schema operates.
     * @param schema      the schema for the message type.
     * @return the previously registered schema, or {@code null} if the given schema was successfully
     * registered.
     */
    public Schema<?> registerSchema(Class<?> messageType, Schema<?> schema) {
        checkNotNull(messageType, "messageType");
        checkNotNull(schema, "schema");
        return schemaCache.putIfAbsent(messageType, schema);
    }

    /**
     * Visible for testing only. Registers the given schema for the message type. If a schema was
     * previously registered, it will be replaced by the provided schema.
     *
     * @param messageType the type of message on which the schema operates.
     * @param schema      the schema for the message type.
     * @return the previously registered schema, or {@code null} if no schema was registered
     * previously.
     */
    public Schema<?> registerSchemaOverride(Class<?> messageType, Schema<?> schema) {
        checkNotNull(messageType, "messageType");
        checkNotNull(schema, "schema");
        return schemaCache.put(messageType, schema);
    }

    private Protobuf() {
        schemaFactory = new ManifestSchemaFactory();
    }

    int getTotalSchemaSize() {
        int result = 0;
        for (Schema<?> schema : schemaCache.values()) {
            if (schema instanceof MessageSchema) {
                result += ((MessageSchema) schema).getSchemaSize();
            }
        }
        return result;
    }
}
